Learning Python @kabirbaidhya

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Introduc on

What is Python?

Python is a programming language that lets you work quickly and integrate systems more effectively. www.python.org “ “

Why Python? 1. Easy to learn yet very powerful 2. General purpose language that could be used almost everywhere 3. Flexibility and scalability 4. Multi-paradigm: object oriented, functional, procedural etc. 5. Popular language, big community 6. Fun to work with 7. Career Opportunities

Python is everywhere CLI applications Web Apps backened / APIs GUI applications Network applications System Administration / DevOps Scienti c Applications Data Science Projects Machine Learning / Deep learning and much more

Ge ng Started

Python 2 or 3? There are two versions of python currently in use python 2.7 & python 3. So, begineers often come up with question “Should I choose Python 2 or Python 3”?

Current State 1. Most production applications today use Python 2.7. 2. Python 3 is ready for the production deployment of applications today. 3. Python 2.7 will only receive necessary security updates until 2020. 4. The brand name “Python” encapsulates both Python 3 and Python 2.

So... 3? Yes, start with python 3.x but familiarizing yourself with Python 2.7 will be very useful. In case if you have to work with legacy projects in the future you might need to know 2.x too.

Installa on Linux Python comes out of the box in most modern linux distros like Debian, Fedora, Centos etc. In case it's not preinstalled you can always download it from the of cial website. Windows You can download the installer from the of cial website. https://www.python.org/downloads/

Code Editors You could use any code editors out there to write code in python as long as it supports syntax highlighting. Here are some recommended editors/IDEs: Microsoft Vscode Atom Sublime Vim Jetbrains PyCharm IDE

Python Basics

Hello World Hello World in python is just a one liner. print "Hello, World!" Pretty neat. Isn't it?

Hello World: Python 3 In python3 it's print("Hello, World!") Mind the parenthesis. In python3 print is a function.

How'd you run it?

1. Directly in the Python shell. Run python shell rst. ➜ python Python 2.7.12 (default, Nov 19 2016, 06:48:10) [GCC 5.4.0 20160609] on linux2 Type "help", "copyright", "credits" or "license" for more informa >>> Then >>> print "Hello World!" Hello World!

2. Standard approach Create a le hello_world.py with the code. print "Hello World!" Now run it with python. ➜ python hello_world.py Hello World!

How it works?

Compila on & Interpreta on Python is a dynamic language, and running it from the command line essentially triggers the following steps: 1. The source is compiled the rst time it is encountered (e.g., imported as a module or directly executed). This step generates the binary le, with a pyc or pyo extension depending on your system. 2. The interpreter reads the binary le and executes the instructions (opcodes) one at a time. From http://security.coverity.com/blog/2014/Nov/understanding-python-bytecode.html

Syntax and seman cs

Incase you're from a C‐style language You need to be aware of few things in python. 1. No semicolon 2. No curly braces 3. Indentation is a part of syntax 4. Dynamically-typed language

Pythonic code Looks something like this """ Generates Fibonacci series upto n """ def fib(n): a, b = 0, 1 while a < n: print a a, b = b, a+b fib(1000)

Let's dive into the code

Example 1: Prin ng and Comments # This prints Hello World! print "Hello World!" # This is a comment; single line comment """ And this is a multiline comment. As this could take more than one line of comments. Like this. """ print "Hello Again." Output: Hello World! Hello Again.

Example 2: Prin ng More # Printing more texts print "Hello World!" print "Hello Again." print "We enjoy typing." print "Learning python is easy." print "And fun." print "Printing text is way easier." Output: Hello World! Hello Again. We enjoy typing. Learning python is easy. And fun. Printing text is way easier.

Example 3: Prin ng more than just texts print "One + One =", 1 + 1 print "One - Two =", 1 - 2 print "Two * Five =", 1 * 5 print "Four / Two =", 4 / 2 print "Expression (12 * 5) - (2 ^ 3) + (1 / 2) =", ((12 * 5) - ( print "Seven is less than or equal to Six is", 7 <= 6 Output: One + One = 2 One - Two = -1 Two * Five = 5 Four / Two = 2 Expression (12 * 5) - (2 ^ 3) + (1 / 2) = 52 Seven is less than or equal to Six is False

Example 4: Variables and Prin ng first_name = "Kabir" last_name = "Baidhya" dob = "July 30, 1992" home_town = "Kathmandu, Nepal" print "Hi! I am", first_name, last_name, "." print "I was born on", dob, "." print "I'm from", home_town, "." Output: Hi! I am Kabir Baidhya . I was born on July 30, 1992 . I'm from Kathmandu, Nepal .

Example 5: Proper Forma ng first_name = "Kabir" last_name = "Baidhya" dob_month = "July" dob_day = 30 dob_year = 1992 difficulty = "easy" print "Hi! I am %s %s." % (first_name, last_name) print "I was born on %s %d, %d." % (dob_month, dob_day, dob_year) print "Python is %s to learn." % difficulty Output: Hi! I am Kabir Baidhya. I was born on July 30, 1992. Python is easy to learn.

Example 6: User Input print "What is your name?", # This would take input from the user # and store it in a variable. name = raw_input() print "Hi! %s. \nIt's nice to meet you." % (name) print "Hope you're doing good." Output: What is your name? Kabir Hi! Kabir. It's nice to meet you. Hope you're doing good.

Data Types

Buit‐in Data types Numeric: int, oat, long Boolean: bool Sequences: str, list, tuple, bytes Mappings: dict Sets: set, frozen set Read more https://en.wikibooks.org/wiki/Python_Programming/Data_Typ es

Immutable & Mutable types 1. Immutable types int, oat, long, tuple, byetes, frozen set, etc. 2. Mutable types list, dict, set, etc.

Example 7: Basic data types an_integer = 6 a_floating_point = 17.60 a_boolean = True a_string = "Foo" print "Integer value = %d" % an_integer print "Float value = %f" % a_floating_point print "Boolean value = %r" % a_boolean print "String value = %s" % a_string Output: Integer value = 6 Float value = 17.600000 Boolean value = True String value = Foo

Example 8: Lists fruits = ['Banana', 'Apple', 'Lime'] numbers = [1, 2, 3, 4, 5, 6, 7, 8] # This is called list comprehension even_numbers = [x for x in numbers if x % 2 == 0] print "Numbers: %s" % numbers print "Even Numbers: %s" % even_numbers print "Fruits: %s, %s and %s" % (fruits[0], fruits[1], fruits[ Output: Numbers: [1, 2, 3, 4, 5, 6, 7, 8] Even Numbers: [2, 4, 6, 8] Fruits: Banana, Apple and Lime

Example 9: Dic onaries data = { "name": "Kabir Baidhya", "dob": "July 30, 1992", "home_town": "Kathmandu, Nepal" } print "Hi! I am %s." % data["name"] print "I was born on %s." % data["dob"] print "I'm from %s." % data["home_town"] Output: Hi! I am Kabir Baidhya. I was born on July 30, 1992. I'm from Kathmandu, Nepal.

Read More? 1. http://docs.python-guide.org/en/latest 2. https://www.python.org 3. https://iluxonchik.github.io/why-you-should- learn-python/ 4. https://learnpythonthehardway.org/book/

Any Ques ons?

Thank You @kabirbaidhya kabirbaidhya@gmail.com The slides were created using Marp. https://yhatt.github.io/marp/